|MadSci Network: General Biology|
It is true that soft drinks are very acidic (the pH of most carbonated beverages is about 3.0) (Potter and Hotchkiss, Food Science, 5th edition). The pH of the food that leaves the stomach is about 2.0, so the soft drinks are less acidic than stomach contents. This means that the soft drink would be further acidified in the stomach. The stomach has a remarkable capacity to adapt to a variety of foods with few side effects. In most people, the acidity of the food eaten has very little effect on the stomach. Soft drinks also are fairly high in sugar, with a sugar concentration of about 12% (Potter and Htochkiss, Food Science, 5th ed.) and many also contain caffeine. If you only infrequently consume foods that are high in sugar or that contain caffeine, the symptoms you note may be related to them rather than to any effect on your stomach. A rapid increase in blood sugar may make a person feel somewhat "unsettled" for a few minutes. Similarly, caffeine may do the same in a person who is not accustomed to consuming it. There is no indication that consumption of soft drinks has any short-term or long-term harmful effect on the stomach in healthy people. If there were, the FDA would be obligated to remove the products from the market.
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